I want to put 33x12.5x15 on my B with aftermarket rims 15x10

I found a chart here by doing a search and it said that the largest tires for a 91 with a 2" lift is 33" so I should be fine, but what back space on the rims should I get?

 

Are you planning to re-gear axles when you do this? If not, be prepared to lose mileage and "umph".

OEM backspacing a between 4.5" and 4.67" and it is a little deep for 33's. 4" to 4.25" is better. I ran 33's on 92 & 93's (front clip styling change) and actually had good luck with 3.5 to 3.75" backspacing without fender rub. 91 should be fine with that as well as I believe there is a bit more room in the front with the earlier style front clip.

 

Also you don't need 10" wide wheels for a 33x12.50........8" are actually better.....especially if you plan on wheeling it any.......they stay on the rim better

 

I have 33x12.50 on 15x10 rims on stock suspension with no issues at all. Cant say as to what back spacing I have though

 

My current tires are 29". Wouldn't a larger diameter slow the rpms down?

 

the General brand tires I am looking at call for 8.5" to 11" rims. I will be doing more street driving than wheeling.

 

Yes larger tires will have a negative effect on your MPG and power unless you re-gear as Greystreak mentioned.

 

33x12.5 may give you a little rub at full turn on standard rims, some people do - some don't. Mine did.

 

Depends on the rim back spacing

 

I think i have the stock aluminum magnum rims on my 35x12.5 and i get rub on a full turn but i don't really turn that hard often and if i do it is usually while going slow.

 

That's why I mentioned "standard rims", by changing my rims with a different back spacing I no longer have that problem. But you also have to be carefull, without a body lift the new wheels would have rubbed on the fenders.